Human behavioral and primate neurophysiological experiments are proposed to extend understanding of the neural mechanisms which the visual system uses to account for eye movements in determining location of seen objects. In human work, subjects use ballistic arm movements to show that nonvisual eye position information remains useful in visual localizations when: 1) target luminance is reduced to attempt to temporally desynchronize neural analogues of retinal image position and eye position information and 2) visual backgrounds are present to permit localization based on visual input. These conditions answer recent objections ruling out a mechanism using nonvisual eye position signals. This work is extended in lesion studies of posterior parietal cortex to show that monkeys cannot control eye position in total darkness or judge target position without visual cues, both tasks that require nonvisual eye position signals. Single cell recordings will also be made in Area 7 of behaving monkeys to determine quantitatively how eye position and velocity is encoded by eye movement neurons known to be found there, and also the nature of visual input to these neurons. The goal is to determine where and how the brain combines eye position and retinal information, to understand vision and visual localization.